1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device.
2. Description of the Related Art
A process of manufacturing a semiconductor device includes a lithography step of transferring by exposure a circuit pattern formed on an original onto a substrate. In the lithography step, the original and substrate are fixed on an original stage and substrate stage, respectively, and these stages are driven in synchrony by linear motors, thereby performing exposure. Recently, in order to improve the productivity and operating ratio of such an exposure apparatus, its size and operating speed have been increased. Along with such increases in the size and speed of the exposure apparatus, a safety measure for its built-in stages is becoming complex.
In the conventional exposure apparatus, an apparatus power source is disconnected as soon as a power shutdown signal is transmitted when a power shutdown switch or emergency stop switch is turned on. To stop a traveling stage in the exposure apparatus, a linear motor used to drive the stage is stopped by, for example, a regenerative brake.
Japanese Patent Laid-Open No. 2001-60614 discloses an exposure apparatus having an emergency stop switch of a two-step structure formed by a first-step switch for activating a brake mechanism, and a second-step switch for activating a power shutdown device. In the exposure apparatus disclosed in Japanese Patent Laid-Open No. 2001-60614, when the emergency stop switch is turned on, the power shutdown device stops power supplied from a power source to a power driving system and the brake mechanism. The emergency stop switch has a two-step structure formed by the first-step switch for activating the brake mechanism, and the second-step for activating the power shutdown device, so that these two switches are activated with a predetermined time lag sufficient to stop traveling of a stage. First, the brake mechanism performs brake control of the power driving system as the first-step switch is activated. The second-step switch is activated a predetermined time after the activation of the first-step switch so that the power shutdown device stops power supplied from the power source to the power driving system and brake mechanism. Therefore, the power supply to the power driving system is stopped after traveling of the stage is stopped.
In the prior art, as soon as the power shutdown switch or emergency stop switch is turned on, an apparatus power shutdown request is enabled, and the power source of the apparatus main body is stopped. After the power supply from the power source to the linear motor is stopped, the regenerative brake is activated to stop the linear motor. In this case, the linear motor may damage upon colliding against, for example, its mechanical stopper depending on the position, moving velocity, and moving direction of the stage. In particular, since a stage with high inertia is operated at high speed along with increases in the size and complexity of the exposure apparatus, the risk of such damage is increasing.
The exposure apparatus disclosed in Japanese Patent Laid-Open No. 2001-60614 uses a time lag of, for example, several hundreds of milliseconds between the activation of the brake mechanism and that of the power shutdown device. The stage may travel at high speed in activating the brake mechanism, and it may still travel at high speed even in activating the power shutdown device. To avoid this situation, the stage can be urgently decelerated within a predetermined time lag by changing the brake condition of the brake mechanism. However, the urgent deceleration may impose a heavy load on the stage, resulting in its deformation.